Hobbing machine



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Aug. 19, 1958 HOBBING MACHINE 6 Sheets-Sheet 5 Original Filed April l2,1949 Aug. 19, 1958 O. E. STAPLES ETAL HOBBING MACHINE l Original FiledApril 12, 1949 6 Sheets-Sheet 6 INVENTORS Or/s E. Sr/vues Array/ventUnited StatesPatent O HOBBING MACHINE Original application April 12,1949, Serial No. 86,952, now Patent No. 2,700,324, dated January 25,1955.

Divided and this application July 7, 1954, Serial No. 441,794

The present invention relates to machine tools and more particularly tomachines for hobbing gears and the like and, particularly, to hobbingmachines of the axial feed type as distinguished from tangential feedtype hobbing machines. The instant application is a division ofapplication Serial No. 86,952, now Patent 2,700,324 issued January 25,1955.

An important object of the invention is the provision of a new andimproved hobbing machine of the axial feed type having a verticallymovable work head and a novel compact driving mechanism for moving theWork head comprising a cooperating lead-screw and nut the former ofwhich is fixed against axial movement in the base of the machine whilethe latter is supported against axial movement in the housing of thework head with either or both being driven to selectively causerelatively rapid travel of the work head or relatively slow travel ofthe work head, this latter travel being in timed relation with therotation of the work spindle and hob arbor.

Another object of the invention is the provision of a hobbing machine ofthe axial feed type having a vertically movable work head and a noveldriving mechanism for moving the work head, which mechanism comprises acooperating screw and nut the former of which is xed to the base of themachine while the latter is rotatably supported in the housing of thework head and wherein the nut is driven by a motor carried by the workhead housing for causing relatively rapid travel of the work head and bythe motor which drives the work spindle and 'the hob arbor for causingrelatively slow travel or feed of the work head in timed relation withthe rotation of the work spindle and hob arbor.

Another object of the present invention is the provision of a novelmachine having an upright column supporting a tool head, a work headmovable vertically along guides on the column, the work head including awork holding spindle and a screw mechanism for moving the work headvertically, the screw `mechanism being located to the outside of thework lspindle with respect to the upright column, to minimize theoverhang of the work head whereby greater accuracy in cutting iseffected.

The invention resides in certain steps of procedure, constructions andcombinations and arrangements of parts, and further objects andadvantages will be apparent from the following description of thepreferred embodiment described with reference to the accompanyingdrawings forming a part of this specification, in which similarreference characters designate corresponding parts, and in which Fig. 1is a side elevational view of a hobbing machine embodying the presentinvention;

Fig. 2 is a front view of the hobbing machine shown in Fig. l;

Fig. 3 is a fragmentary enlarged view, partly in section, of the hobbingmachine of Fig. 1, showing the work spindle and elevation mechanism forthe work head,I the section being taken substantially on line 3--3 ofFigs. 4 and 5;

2,847,910 Patented Aug. 19, 1958 ICC Fig. 4 is a sectional view takensubstantially on line 4 4 of Fig. 3;

Fig. 5 is an enlarged sectional view taken substantially along line 5--5of Fig. 4; and

Fig. 6 is a sectional view taken substantially along line 6-6 of Fig. 5.

Although the invention is susceptible of various modiiications andalternative constructions, it is herein shown and described as embodiedin a hobbing machine generally of the type shown in United States PatentNo. 2,307,428, issued January 5, 1943, except that, among other things,the shape of the machine is slightly different, for example, the hobhead is carried by a member slidably supported in a cylindrical aperturein the vertical column or frame rather than bemg supported on horizontalways, and the mechanism for moving the work head vertically is of adierent arrangement.

Generally speaking, the machine is of vertical construction andcomprises a base A, a vertical column or gooseneck B supported upon thebase A, a work head C .vertically movable upon vertically spaced pairsof ways 10, 10 on the column B, and a tool or hob head D carried by acylindrical member slidably supported in the column B and adjustabletherein horizontally toward and from the work head. The workpiece to behobbed, which may be a gear blank, a shaft to be splined, or the like,is supported for rotation by a work spindle 12, forming a part of thework head C, and a tail center 13 carried by a tail slide 14 supportedfor movement toward and from the work spindle upon ways 15, 16 on anoutboard column 18 constituting a part of the work head. A hob arbor 17is rotatably supported in the hob head D, and during operation of themachine is rotated in timed relation to the rotation of the work spindle12 by a cut .motor CM located in the lower part of the column B andoperatively connected to the arbor and work spindle. The workpiece ismoved vertically past the hob during the cutting operation to elect thenormal feeding operation, by vertical movement of the work head C, whichmovement is timed with the rotation of the hob arbor. Simultaneouslywith the other movements and in timed relation therewith, the arbor ismoved axially to advance the unused portions of the hob, which isindicated at H in Figs. l, 2 and 3, into cutting relation with theworkpiece, which workpiece is rotated in a direction such that theperipheral portion engaged at any instant by the hob moves in adirection opposite to that of the axial movement of the hob. Rapidtraverse means, including a reversible rapid traverse motor TM, isprovided to cause relatively rapid movement of the work head to carrythe workpiece from a work loading position to the cutting position andto return the work head to the loading position after the cuttingoperation has been performed.

The structure of the hob head is described in detail in the aforesaidapplication and will not be repeated herein since it is not necessaryfor an understanding of the present invention. Sutiice it to say thatthe hob head D is supported on the column B for horizontal movementtoward and away from work supported on the work spindle 12 and forangular movement in a Vertical plane. The horizontal positioning of hobhead D is controlled by rotation of a dial 19 on column B while theangular positioning is controlled by` turning a rotatable member 27. Thehob arbor 17 is rotated by the cut motor CM through a main drive shaft55 journalled in the column B and which has a pulley 57 mounted thereonwhich is driven by the cut motor through a belt. The main drive shaft 55is adapted to drive a parallel, splined shaft 58 which is journalled inthe column B and is supported in a gear 60 journalled in a web 61 of acylindrical boss structure 62 which projects from the rear wall ofcolumn B. The gear 60 is driven by a gear 63 mounted on the drive shaft55, and gear 60 is splined to the shaft 58 so that the latter may bedriven throughout the horizontal adjustments of the hob head. Theforward end of the shaft 58 extends into the hob head Ehousing and 'has`a helical gear 64 thereon operatively connected to the arbor drivegear. v

The work spindle 12, which iis tubular in construction, has its upperend Ijournalled by suitable lantifriction bearings in a cylindrical bossformation 70 ionthe work head C, and its lower end is journalled in anantifriction bearing in an opening through the bottom wall of lthe workhead housing 71. Preferably, the work spindle v12 is provided with apneumatically operated chuck for'holding the work pieces. The chuck islnot shown as such chucks are well known, however, a portion of thepneumatic mechanism 72 kfor operating the chuck vis lshown attached tothe lower end of the spindle. The spindle 12 is driven in timed relationto the hob arbor 17 by the cut motor CM, through a drive mechanism whichincludes a verticalshaft 73 the upper end of which is journalled'in thecolumn B and is provided with a helical gear 74 driven by a helical gear78 on shaft 55. The shaft'73 projects downwardly into a channel 79formed inthe column B and is splined throughout a substantial portion ofits length. The splined portion of the shaft 73 is slidably engaged by ahelical gear 80 splined thereto. The gear 80 is journalled in aprojection 81 integral with the housing 71 and which extends into thechannel 79. A cross shaft 83 having one end journalled in the projection81 and the opposite end journalled in a partition wall 84 of the workhead housing, is driven by gear 80 through a gear 85 mounted on the endof the shaft journalled in theprojection. It will be seen that the drivebetween gears 80 and 85 will be maintained throughout the vertical rangeof movement of the work head C by reason of the spline connectionbetween shaft 73-and gear 80.

The shaft 83 drives a speed change gear train, indicated generally at87, which is located within the front compartment 88 formed in the workhead housing 71. The gear train drives a shaft 93, which comprises oneinput element of a differential 94 in the drive for the work spindle`12. Theoutput of the differential 94, comprises a shaft V96'having aworm 97 which drives a worm gear 98 integral with the spindle 12.

The differential 94 comprises a cage 100 carrying four planetary gears101 which gears mesh with two axially aligned sun gears 102, 103 formedon the adjoining ends of the aligned input and output shaft 93, 96,respectively. The cage 100 has a helical gear 104 by which rotation ofthe cage is controlled. When the cage is stationary and shaft 93rotates, shaft 96 will be driven directly. If

vthe cage is rotated, the shaft r96is driven at-a speed which is thealgebraic sum of the speeds of the cage and input shaft 93. When it isdesirable to cut spur teeth on gear blanks, for example, the cage islocked to prevent rotation thereof and the workpiece will be Imoved pastthe hob to effect the cutting of straightgear teeth. yIn the event it isdesired tocut spiral teeth, the cage is rotated to change the' speed ofrotation of the work spindle 12 relative to the movement of the workhead C and cause spiral teeth to be formed, as is well understood bythose familiar with the art.

The work head C, see Figs. 3 and 4 is supported by a screw 107, thelower end of which, in the illustrated embodiment, is non-rotativelyattached to the base A and the upper end of which has a tubular nut 108threaded thereon. Preferably, the screw 107 is enclosed in a`telescoping guard 109, for shielding the screw from chips and otherforeign particles which might otherwise collect on the threads thereof.The nut 108 is journalled at its lower end in an antifrictioncombination thrust bearing 110 mounted in the lower walls of the workhead housing and its upper end is journalledv in bearings 111 mounted ina bracket `112integral'with the partition=84 in the work head housing71. When the nut 108 is rotated, by means described hereinafter, thehead C is moved vertically in a direction depending on the direction ofrotation of the nut. The screw 107 extends through a flanged ring 1113vwhich is mounted in an opening in the lower wall of the work headhousing and bearing is secured in the ring. The inner race of vthebearing 110 is attached to the nut 108.

The nut 108 is adapted to be rotated by either the cut motor CM or thetraverse motor TM, and automatically controlled means is provided forrendering one or the other of the motors effective to drive the nut ,atthe proper times and in the proper direction. The cut motor drivemechanism for the nut 108 includes a worm gear in mesh with and drivenby, a worm 116, shown in Fig. 5, formed on a shaft 114 rotatablysupported in the work head housing 71 and operatively connected'to theshaft 93 by -a speed change gear train 118, -see `Fig. 4. The worm -gearl115 is rotatively mounted on the nut 108 yand-is provided with-adownwardly extending hub 117, Vthe lower portion of which is externallysplined. A clutch collar surrounds the hub 117 and has teethslidinglyengaged with the hub splines for connecting the work gear -115 with thecollar 120 throughout a-range of sliding movement of the collar onthehub. A sleeve 121 keyed to the nut 108 immediately -below thetlowersplinedfend of the hub 117 of the worm gear 11S, has its upper portionsplined as at 122 to receive the internal teeth of the collar 120 whenthe collar is llowered over the upper portion of the sleeve. Thus, bysliding the clutch-collar 120 downwardly and upwardly, as viewed in Fig.7, the Worm 115 is drivingly connected and disconnected, respectively,with the nut 108.

The clutch collar 120 is moved vertically by a yoke 123 which has pins124 extending intoa peripheral groove 125 formedA in the collar. Theyoke is moved by an electrical solenoid 126 which has an armature 127associated therewith and which is connected with a rack member 128 whichcooperates with pinion 129 formed on a rocker shaft 130 torotate thelatter shaft when the armature isvattracted -and released from thesolenoid. An arm 132 on the rocker shaft is connected to the clutch yoke123, and when the solenoid is energized, the yoke is lowered, as viewedin Fig. 5, for connecting gear 11S with the'nut 108. When the solenoidis deenergized, the armature-drops and the yoke. is raised to disconnectthe -gear 115 and nut 108. The solenoid 126 is controlled by a suitablecontrol circuit,-not shown, according to the verticalposition of thework head C relative to the hob head.

The traverse motor TM is mounted on the exterior of the left hand wallof housing 71, as viewed in Fig. 5, and it is drivingly connected withthe nut 108 by a shaft 133 connected to the motor armature shaft andjournalled in a bearing housing 134. A helical gear 135 connected to theend of shaft 133 opposite the motor, is continuously in mesh with ahelical gear 136 formed integral with the nut 108. The traverse motor isconnected in driving relation with the nut 108 at all times, and it isadapted to rotate the nut at a rapid rate, relative to that at which thenut is driven by the cut motor, for moving the work head C vertically tocutting position and to return the work head to loading position. Thecontrol system for the hobbing machine is arranged such that when thenut 108 is driven by gear 115, the traverse motor is deenergized and itmay be driven through the gears 135, 136.

When the bobbing machine is used to cut spiral gear teeth, or the like,the cage 100 of the differential 94 is driven in timed relation to therotation of the nut'108, as` shown, the cage100 is-operatively connectedto the nut 108 by drive mechanism which includes miter gears 140, 141 onthe upper end of the nut 108 and a horizon- --tally extending-shaft142,v respectively,-seen in Fig. 5.

The shaft 142 is adapted to drive a speed change vgear saisie train 143located in a compartment formed in the side of the workhead housing 71and opposite the rapid traverse motor. The gear train 143 drives a shaft144 having a helical gear 145 thereon which drives the gear 104connected to the cage 100. The rotation of the cage 100 imposes adiiferential in speed between the input shaft 93 and the drive shaft 96for the spindle 12 according to the speed of the nut 108. If it isdesired to cut straight gear teeth, or the like, the gear train 143 isdisconnected and the cage 100 held against rotation with the result thata direct drive is had through the differential.

It will be seen that as the workpiece is fed vertically past the hob,the piece is rotated on its axis at a certain speed relative to thespeed of the hob, and the rate of vertical feed of the workpiece has adefinite relationship to the hob speed.

In operation of the machine, a new or sharp hob is mounted on the arbor17 and the latter is drawn upwardly so that the end of the hob willinitially engage a workpiece mounted in the spindle 12. The workpiece ischucked in the spindle 12 and secured therein by the tail stock member13 and the hob head D is adjusted horizontally so that when it engagesthe workpiece it will cut to the proper depth. It is to be understood,of course, that the hob head D will be rotated or positionedapproximately 90 from the position shown in Figs. l and 2 so that theaxis of the hob will extend transverse with respect to the axis of theworkpiece. For purpose of explanation, it will be assumed that themachine is set for conventional hobbing and that the workpieces areloaded when the work head is in its lowest position. The automaticcontrol of the cut motor, the rapid traverse motor and the solenoid 125may be effected by a control system, parts of which are shown at 165 and166, and which may be similar to that described in the aforementionedpatent and in which case the solenoid 126 would be connected in thecontrol circuit in such a manner that it would be energized anddeenergized simultaneously with the energization and deenergization ofthe rapid traverse motor. The cycle of operation is initiated byactuation of the start push button switch 165 which causes the traversemotor to rapidly elevate the work head C to a point at which theworkpiece closely approaches the hob. The traverse motor is thenautomatically deenergized and the clutch solenoid 126 is energized toconnect gear 115 with the nut 10S so that the work head C will continueto move vertically but at a relatively slow rate past the hob H whilethe hob and workpiece both rotate in timed relation. After the workpieceis moved past the hob, the clutch solenoid and the cut motor areautomatically deenergzed and the iinished work is removed from thespindle 12, after which the start push button switch 165 is againdepressed thereby causing the traverse motor to operate in a reversedirection from its initial direction to rapidly lower the Work head C tothe loading p0- sition, at which point the traverse motor isautomatically deenergized. A new workpiece is mounted to the work headand the cycle of operation is repeated as described.

As is explained in detail in the aforesaid application, during thecutting operation the hob H is continuously advanced in the directionwhich is counter to the direction of movement of the periphery of theworkpiece at its point of engagement with the hob so that unusedportions of the hob Will be continuously fed into tangential engagementwith the workpieces and the initial engagement of the unused portionswith the workpieces will be with portions of the work which have beencut by used portions of the hob. In other words, the used portions ofthe hob will rough out the cuts and the less used portions will performthe finished cuts so that greater accuracy is achieved in the finishedworkpiece and at the same time a maximum useful life ofthe hob isattained.

It should be noted that the screw 107 on which the work head C is movedvertically is located on an axis which is substantially at the center ofmass of the work head C so that a minimum of stress is applied to theguides 10, 11, 15 and 16, which increases the accuracy and durability ofthe machine. This arrangement also permits the work spindle 12 to belocated adjacent to the column B which provides a minimum of overhang ofthe work head and provides greater stability for the spindle. Inaddition, the structural arrangement shown provides a relatively compactdriving mechanism for rotating the work spindle 12, the hob arbor 17 andthe elevating nut 108 or lead screw 107.

Suitable means may be provided for lubricating the various gears andbearings and a suitable coolant may be fed to the hob and workpieces,but since such means are commonly used, they have not been shown in theembodiment of the invention described.

While the preferred form of the invention has been described inconsiderable detail, it is to be understood that this is by way ofexample only and that the invention is not limited to the particulardetails shown and described.

Having thus described our invention, we claim:

l. In a hobbing machine, a frame, a tool spindle rotatively supported bysaid frame, a work head including a work spindle supported for verticalmovement with respect to said frame, means for moving said work headvertically comprising cooperating nut and vertical lead screw elements,means connecting said lead screw element to said frame below said Workhead and for supporting said lead screw element-against axial androtative movement, means for rotatably connecting said nut to said workhead and for transmitting translatory movement of said nut to said workhead, power actuated means including a gear train for rotating said workspindle and said tool spindle in timed relation, and means foroperatively connecting said nut element to said gear train for rotationthereby and including a clutch member movable to engage or disengage thedrive to said nut element from said gear train, and a motor on said workhead operatively connected to said nut element for relatively rotatingthe same at a relatively rapid rate.

2. In a hobbing machine, a frame, a tool spindle rotatively supported bysaid frame, a work head including a work spindle supported for verticalmovement with respect to said frame, means for moving said work headvertically comprising a relatively rotatable cooperating nut andvertical lead screw elements, means connecting said lead screw elementto said frame and for supporting said lead screw element against axialmovement, means for connecting said nut element to said work head totransmit axial translatory movement of said nut element to said workhead, means including a gear train for rotating said work spindle andsaid tool spindle in timed relation, means for operatively connectingone of said nut and lead screw elements to said gear train forrelatively rotating said nut and lead screw elements including a clutchmember movable to engage or disengage the drive to said one element fromsaid gear train, power actuated means operatively connected to said nutand lead screw elements for relatively rotating said nut and lead screwelement at a relatively high speed, and means operable to disengage saidclutch member upon operation of the last-said power actuated means.

3. In a machine tool, a frame; a work head mounted for vertical movementon the frame; a work spindle; means for moving the work head verticallycomprising, a screw mounted on said frame; a nut threaded on the screwand rotatably connected with said head for moving the latter; a drivefor rotating the nut; a motor for operating said drive; and means forrotating said work spindle comprising, a diiferential, one input elementof said diiferential being driven by said nut and the other inputelement of said differential 'being driven by said motor.

(References on following page) 7 References Cited ip the tle of this`patent 2,231,866 2,375,172 UNITED STATES APATENTS 2,736,243 1,278,867Daneke ,Sept. 17, 1918 1,889,930 Morton Dec. 6, 1932 5 l2,157,471Armitage May 9, 1939 127,185

8 Adams Feb. 18, v1941 Arter May 1, 1945 Armitage et al. Feb, 28, 1956FOREIGN PATENTS Austria Mar. 10, 1932

